In general, a water pump motor is used to drive a water pump that is installed in a drain water tank of a washing machine or is used as a driving source of a water pump that is used for circulation of a coolant that cools an engine. A water pump equipped with the water pump motor works under an environment that the inside of the water pump always directly contacts water.
Thus, a motor pump having a mechanical seal structure or a canned motor pump having a canned cover structure for sealing a stator is used for the purpose of protecting a motor from water when the water of the inside of a water pump is drained to the outside of the water pump or in order to prevent failure of bearings or shortened life of belts due to leakage of a coolant.
U.S. Pat. No. 4,277,115 proposed the canned motor pump, in which a canned cover seals only a stator and thus a rotor soaks in water. Accordingly, durability of a bearing to support a rotational shaft is adversely affected. In addition, an optimal magnetic gap cannot be maintained because of a canned cover that is placed between the rotor and the stator, to thereby cause a low efficiency.
In addition, since the rotor soaks in water in the canned motor pump, rotation of the rotor is affected to thus decrease a motor efficiency.
Moreover, since a conventional motor pump has a structure that the axis of rotation of the impeller is integrally formed with the axis of rotation of the motor, a motor assembly and a pump assembly may not be independently assembled and tested, to thus cause a low assembly productivity problem.
In addition, when the canned cover for use in the canned motor pump is molded by using a PPS (PolyPhenylene Sulfide) material and then assembled with a stator, there is a problem that the canned cover is not easily combined with a stator core.
Furthermore, according to the conventional art, the outside of the stator employs a double sealing structure. Here, the outside of the stator is insert-molded, by using BMC (Bulk Mould Compound) and is simultaneously sealed by a canned cover using a PPS sealing material, to thus cause a manufacturing cost to increase.